The specific aim is to study the pathophysiology of compartment syndromes by correlating muscle-compartment fluid pressure, as measured by the wick catheter, with long-term tests of muscle and nerve function. Additonally, the effects of intracompartmental pressure amplitude and duration on myoneural necrosis will be evaluated during shock. These basic correlates will be applied to clinical cases of compartment syndromes. Our previous investigations indicate that significant intracompartmental damage is produced at a threshold-pressure level and duration of 30 mm Hg and 8 hours. However, this tissue damage may represent injury which is reversible during subsequent regeneration. Long-term tests of muscle and nerve function will provide objective criteria for defining a matrix of pressure-time variables which produce irreversible necrosis. Presumably these threshold pressure-time variables will change in trauma patients suffering shock since their capillary-filling pressure is probably diminished during hemorrhagic hypotension. Presently, there is no general agreement regarding a threshold level, above which muscle is jeopardized. The studies outlined in this proposal should yield sufficient data to determine a matrix of threshold-pressure parameters which produce irreversible, myoneural dysfunction. Muscle function, as determined by contraction force, will be correlated with sequential muscle biopsy samples examining time-course changes in muscle morphology, fiber types, enzymes, and other biochemical parameters. After pressurization, intracompartmental nerve function will be quantified by electromyography for a period of one month, after which intracompartmental nerves will be removed and examined microscopically. The effect of shock on myoneural necrosis after compartmental pressurization will be studyied by technetium-99m stannous pyrophosphate uptake, other biochemical indices of necrosis, and long-term tests of myoneural function. Patients with acute and chronic compartment syndromes will be studied by the wick technique. Recently-developed ultrasonic scanning techniques will allow us to correlate changes in compartmental volume and pressure with exercise. These latter studies should significantly aid the diagnosis of chronic compartment syndromes in humans.